Osteoarthritis, one of the types of arthritis, is also referred to as degenerative arthritis. It is said that osteoarthritis is an arthritis caused by degenerative changes in the cartilage and adjacent bone in the synovial joints. That is, osteoarthritis is characterized by gradual loss of articular cartilage, combined with thickening of the subchondral bone, bony outgrowths at the joint margins, and nonspecific synovial inflammation. Osteoarthritis is caused by cartilage damages according to aging and/or physical stresses (for example, obesity, trauma, etc.). Therefore, osteoarthritis involves severe pain and/or movement disorder in the weight-bearing joints, such as knee joint and hip joint; and the negligence thereof for long time results in joint malformations.
Typically, osteoarthritis is progressed in the following steps: the cartilage change phase in which edema occurs by the increase of water contents in the cartilage (step 1); the fibrillation phase in which the cartilage is destructed, thereby resulting in erosion of the cartilage surface, bone exposure, and narrow articular cavity (step 2); the overall cartilage reduction phase in which, although chondrocytes initiate compensatory cartilage formation, cartilage breakdown occurs faster than cartilage formation (step 3); the bone malformation phase in which the bone modification results in joint malformations and dysfunctions (step 4); and the changes of articular soft tissue in which the soft tissue become thickened (step 5).
Rheumatoid arthritis, which belongs to a different type of arthritis from osteoarthritis, is a chronic autoimmune disease characterized by inflammation and proliferation of synovial cells; and causes osteoporosis and bone erosion around in the joints, unlike osteoarthritis. Typically, rheumatoid arthritis is progressed in the following steps: inflammation in the synovial membrane spreads to joint capsules, ligaments, tendons, etc (step 1); progressive destruction of joint cartilage leads to narrowing the joint space and destroying tension of both joint capsule and ligament (step 2); inflammation infiltrates into bone, thereby inducing partial bone erosion (step 3); and functional disability is caused in the joint (step 4). Therefore, rheumatoid arthritis and osteoarthritis are quite different in their etiologies and progressions, and therefore the therapeutic methods thereof are also different.
The treatment of osteoarthritis used in the prior arts includes the use of therapeutic agents, for example acetaminophen, tramadol, nonsteroidal antiinflammatory drugs (NSAIDs), diacerin, glucosamine, etc. Among them, the NSAIDs have been reported to induce side effects in the gastrointestinal tract, such as gastric ulcer, duodenal ulcer, etc. Therefore, when these drugs are applied to a patient suffering from osteoarthritis and potential problem of gastrointestinal side effects, a cytoprotective agent (e.g., rebamipide, etc), a H2-receptor antagonist (e.g., cimetidine, ranitidine, etc), and/or a proton pump inhibitor (e.g., omeprazole) are also co-administered.